Female Peregrine Falcon Falco peregrinus replaces an incubating female and raises her young

Systematic observations were conducted on the breeding cycle of a pair of Peregrine Falcons Falco peregrinus near Canberra, A.C.T., in spring 1992. The adult female Peregrine disappeared from its nest site around the time that young hatched. Nestlings were raised by the male and a new female. There were indications of food shortage at this nest and we discuss whether this could relate to the disappearance of the original female.